What do you know about preserving lemons? Your favorite way to 
preserve them? Interesting ways to use them?

-- Dani

I, myself, have never made preserved lemons, but here is what I have been able to find out.  According to The New Food Lover's Companion, the lemons are "preserved in a salt-lemon juice mixture (sometimes with spices such as cinnamon, cloves and coriander) for about 30 days. Preserved lemons have a silken texture and a distinctive flavor. They're an indispensable ingredient and flavoring in Moroccan cooking".  Bacteria and yeasts acting on the lemons soften the rinds and deepen the flavor.

In Jewish cooking, there are two broad traditions, Ashkenazi and Sephardic.  Because Sephardic Jews are descended from those of Spain and Portugal, and because of the influence of Northern African cooking on the foods of those countries, preserved lemons show up in Sephardic cooking, too.

Recipes for preparation vary, but most commonly use unwaxed lemons, salt and lemon juice.  If there is any chance that the lemons have been waxed, then they should be well washed to allow the preserving liquid to enter the skin.  The lemons are cleaned and cut, and the cuts are salted,  They are then packed into a container that can be tightly sealed, alternating with salt and covered completely with fresh lemon juice.  Typically, about 1 tablespoon of salt is needed per lemon.  Kosher, pickling or sea salt without additives should be used.  If used, the spices are added as the lemons are packed into the container.

Some recipes seal the container at this point, others cover the liquid with 1/4 inch, or so, of olive oil, and still others wait a week or so and then add the olive oil.  In all cases, the lemons are allowed to age three or four weeks in a cool location.  If the lemons are frozen and then thawed beforehand, the preparation time can be shortened substantially.

Instructions vary on how the lemons should be sliced.  In the simplest recipes they might be halved or quartered.  In one, the ends are cut off exposing the pith.  the lemon is then cut lengthwise about 3/4 of the way through, and then cut lengthwise from the other end, again 3/4 of the way through, but turned 1/4 turn from the first cut.

The Larousse Gastronomique gives the following recipe for preserved lemons:

Wash 1 kg (2 1/2lb) untreated lemons, wipe and cut into thick round slices.  (Small lemons can simply be quartered lengthwise.)  Dust with three tablespoons of fine salt and leave them to discharge their juices for about 12 hours.  Drain them, place in a large jar, and cover them completely with olive oil.  Leave in a cool place for a month before use.  Close the jar firmly after opening and keep in a cool place away from light.

In all methods, there is some risk of contamination of the lemons by harmful bacteria so care must be taken in preparing and consuming preserved lemons.  Preserved lemons are also prone to developing a white stringy mass, similar to Mother of Vinegar, that is not harmful.

Preserved lemons can be used in dishes such as tagines, in salads and even as the fruit in a Preserved Lemon Martini.  They can also be used as a garnish to enhance the flavor of hors d'ouvres.